Comparison of init systems
This article [[Article description::compares and contrasts init systems.]] Some of the init systems compared below are available for Gentoo, while others (like launchd and SMF) are not.
Available software
| Feature | Init system | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| sysvinit | OpenRC | upstart | systemd | SMF | launchd | Epoch | finit | runit | BSD rc.d | |
| Supported in Gentoo | partially (used by OpenRC) | Yes (default init) | No | Yes | No | No | Yes | No | Yes | No |
| Package / Bug# | sys-apps/sysvinit | sys-apps/openrc | bug #498376 sys-apps/upstart in unity-gentoo overlay. | sys-apps/systemd | - | - | sys-apps/epoch | - | sys-process/runit | - |
| Supported platforms | Linux / BSD | Linux + BSD | Linux | Linux | Solaris | MacOSX | Linux | Linux | Linux / BSD / MacOSX | BSD |
| Main coding language | C | POSIX shell (+ C) | C | C | C | C | C | C | C | POSIX shell (+ C) |
| Main dependencies | - | init (sysv or BSD) | D-Bus | D-Bus | init(sysv?) | - | libc, /bin/sh | ? | - | rcorder |
| Init script/service format | single config file | shell scripts | config files + shell fragments | config files (ini) | XML (+ shell scripts) | plist | multiple or single .conf | multiple or single .conf | shell scripts | shell scripts |
| Per-service configuration | No | Yes (conf.d) | With in-job mechanisms (normal exit, respawn) | Yes | Yes (service instances) | ? | Yes (v1.1+) | ? | No | No |
| Running as a daemon | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) | Yes (invoked) | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) |
| Cross-service dependencies/events | No | Yes | Yes | Yes | Yes | No | Yes (basic support, v1.3+) | ? | Yes | Yes |
| Parallel service startup | Yes | Yes (optional) | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes |
| Keeping daemons alive | Yes | Yes (optional v0.21+ via supervise-daemon) | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Preferred service file supplier | n/a | Gentoo | Ubuntu | upstream | Solaris | MacOSX | n/a | n/a | Void Linux | NetBSD, FreeBSD, OpenBSD |
| License | GPL v2+ | 2-cl. BSD | GPL v2 | LGPL v2.1+ | ? | Apache License 2.0 | Unlicense | MIT | BSD | BSD |
Supported services (in Gentoo)
| Feature | OpenRC | systemd |
|---|---|---|
| Filesystem mounting | One script per group (root, local, network, swap...). | Two units per mountpoint (fsck + mount), runtime-generated with dependencies. |
| getty (terminal prompts) | Started through /etc/inittab or via agetty script | One unit per console, instantiated from template on-demand. |
| Networking setup | Several options[1] like dhcpcd[2][3], netifrc[4], iwd [5], or NetworkManager.[6][7] | External (NetworkManager, networkd, DHCP daemons). |
| X11 Display Manager setup | Single service for all (required to auto-restart). | Separate DM units. |
See also
- Runit — a daemontools-inspired process supervision suite that also provides a program suitable for running as process 1.
- S6 and s6-rc-based init system — an init system built using components from the s6, s6-rc and s6-linux-init packages
- Nosh — a multi-purpose init and process supervision software package made by Jonathan de Boyne Pollard.
- OpenRC — a dependency-based init system that maintains compatibility with the system provided init program (see the init section).
External resources
References
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